Electric discharge tube comprising a plurality of electron beams



May 21, 1957 G. H. P. ALMA 2,793,310

ELECTRIC DISCHARGE TUBE COMPRISING A PLURALITY OF ELECTRON BEAMS FiledFeb. 3, 1954 CHANNEL a j a Em 1357 GERRIVT HENDRIK PETRUS ALMA AGENT 3.INVENTOR I ELECTRIC DISCHARGE TUBE COMPRISING A PLURALITY F ELECTRONBEAMS Gerrit Hendrik Petrus, Alma, Eindhoven, Netherlands,

assignor, by mesne assignments, to North American Philips Company, Inc.,New York, N. Y., a corporation of Delaware Application February 3, 1954,Serial No. 407,971 Claims priority, application Netherlands February 3,D53

4 Claims. (Cl. 313-69) The invention relates to an electric dischargetube in which a plurality of electron beams are produced, which can bedeflected each into two diflerent positions independently of oneanother. The invention relates more particularly to a selector tube forselecting a definite channel from a plurality of channels.

Such tubes are known per se. A beam may be deflected in a manner suchthat it strikes a particular anode, in which position it is held.Similarly to the mechanical selectors, in which a contact arm is adaptedto perform a rotary movement and an upward movement, the beam is adaptedto move to and fro and up and down. However, such tubes are verycomplicated and use must be made of a beam having a small sectional areain order to avoid excessively large dimensions of the tube. With binarysystems use is therefore frequently made of triodes, of which the triodecorresponding to the selected channel draws current. Although the tubesemployed may be of simple construction, the device is neverthelessinvolved owing to the great number of tubes required with the associatedcircuit elements. Use is frequently made of double triodes.

With calculating machines a choice is to be made frequently from aplurality of, for example, eight channels on the basis of an indicationin the binary system. Then, if double triodes are used, 1+2+4=7 doubletriodes are required with their associated circuits and component parts.

This may now be achieved in a simpler manner by using a devicecomprising a selector tube according to the invention.

According to the invention in such a device comprising an electricdischarge tube having a plurality of electron beams and suitable forselecting one from a plurality of channels on the basis of an indicationin the binary system, the beams may be deflected each into twopositions, independently of one another, each beam strikingsimultaneously a plurality of anodes equal to half the number ofchannels, these anodes being connected for the various beams to thevarious channels in a manner such that in each combination of beampositions for one channel all anodes connected thereto lie alwaysoutside the beams. The channel not conveying current is thus theselected channel.

If desired, the deflection may be effected by means of a grid, so thatthe electrons are allowed to pass to one group of anodes or reflectedtowards the other group. Then a number of systems corresponding to thenumber of binals may be provided in the longitudinal axis of thecathode. By suitable screening of the systems it is possible to ensuretheir independent operation.

In order that the invention may be readily carried into effect, it willnow be described with reference to the accompanying drawing, in whichFig. 1 shows diagrammatically an arrangement of a device in accordancewith the principle of the invention and l atented May 21, 1957 icesimultaneously by a beam. The beam of each system occupies either theposition 0 or the position 1. In the former, it strikes the upper groupof four anodes. In the latter, it strikes the lower group of fouranodes. The beam of each electrode system is separately controlled. Eachchannel is connected to all anodes of the same reference numeral. Forexample, all the anodes designated by the numeral 5, of which one ispresent in each electrode system, are electrically connected together toa common channel, which may also be designated 5. For simplicity, onlyone channel is shown in the drawing, there being, of course, separatechannels for each of the anodes 1 to 8. The anodes are arranged amongthe two groups of each system such that in each combination of beampositions there is always one channel of which the anodes are not struckby a beam. By a suitable arrangement, such a channel, all anodes ofwhich are idle, may be opened. For this purpose use may be madeofvarious arrangements, which are familiar to those skilled in the art.The anodes having the same reference numerals and connected to oneanothenmay, for example, be connected to a grid of a triode, this gridbeing fed by positive voltage via a heavy resistor. If all anodes of thechannel concerned become idle, the said grid becomes more positive,since the said resistor is no longer traversed by the electron flow, sothat the triode becomes conductive.

If the position of the electron beam shown is indicated by 0 and theother position by 1, the combinations indicated in the table at the sideof Fig. 1 are possible for the three beams; it will be observed that ineach position of the beams the anodes of only one channel are idle. Forexample, if the beam in the upper system is in position 1, that of thecenter system in position 0 and that of the lower system likewise inposition 0, it will be noted that of all the anodes 1 to 8, only thethree anodes 5 in the three systems are all simultaneously free frombeing struck by an electron beam; hence, this channel becomes theselected channel. In the table, the three columns to the left indicatethe positions occupied by the beams in the upper, central and lowerelectrode systems, respectively; whereas, the column to the rightindicates the selected channel for those positions of the beam.

A binary system as described above has the advantage that each beam canalways be moved into the one or the other extreme position without theneed for intermediate positions. This provides a very reliableoperation, since the beam position varies only with the polarity of thevoltage at the deflection plate concerned and is independent of thevalue of this voltage within wide limits.

The system shown in Fig. 1 may be arranged in the longitudinal axis of acommon cathode one above the other.

Figs. 2 and 3 show a further embodiment, in which three systems arestacked up around a cathode k, each system comprising four rod-shapedanodes, located inside the second grid and four similar anodes locatedoutside the second grid. This second grid serves as a controlgrid and iscapable of passing the complete electron flow to the anodes outside thisgrid or it is capable of completely reflecting the flow to the anodesinside this grid. The first grid serves as an accelerating grid. Bymeans 3 of screens the systems may be isolated from one another. Such atube has 13 contact pins.

If desired, the various systems may be displaced relatively to oneanother with a view to the positioning of the interconnecting wires ofthe anodes. With a suitable arrangement of the anodes various anode rodsmay extend through two or more systems and thus be constituted by asingle rod, for example, the anodes 1 and 8,.which occur in each systemin a corresponding group, as is evident from .Fig. 1.

Although by way of example a tube comprising three beams is described,the tube being thus capable of selecting from 2 :8 channels, use may, asan alternative, be made of more than three or less than three beams.

A tube having two beams can select from four channels,

atube having four beams from 16 channels, and so on. In general, for nelectrode systems, .2 channels are available, andeach group of anodes ina system struck by a beam in one position is equal to As an alternative,the construction may be varied. The rod-shaped anodes, for example, maybe replaced by plates and the like.

What is claimed is:

1. An electric discharge tube comprising a plurality of electrodesystems; each of said electrode systems including electronbeam-producing means, two groups of anodes, and means for controllingsaid 'beam to strike one or the other of said anode groups; each of saidanode groups including a plurality of anode electrodes, each anodeelectrode of each anode group being interconnected with one anode ofeach of the other systems, said anodes being arranged in the groups ofeach system such that for every combination of beam positions strikingwhole anode groups, only one series of interconnected anodes of thesystems are not struck by any of the beams.

2. An arrangement comprising an electric discharge tube having nseparately controllable electrode systems where n is an integer greaterthan one; each of said electrode systems including electronbeam-producing means, two groups of anodes, and means for controllingsaid beam to strike the whole of one or the other only of said anodegroups, each of said anode groups including independent anodeelectrodes; and 2 channels, each of said channels being coupled to oneanode of each of the electrode systems whereby n anodes are connected toeach channel, said anode electrodes being arranged in the groups of eachsystem such that for every combination of positions of the beams in eachof the systems, only one series of anode electrodes all connected to thesame channel are not simultaneously struck by any of the beams.

3. An electric discharge tube asset forth in claim 1 wherein there isprovided a common elongated cathode for all the electrode systems, saidsystems being arranged adjacent one another in the direction of lengthof the cathode, some of the anodes of the systems being constituted byrod-like members common to at least two of the systems.

4. An electric discharge tube as set forth in claim 1 wherein there areprovided a pair of grids for each of the electrode systems, one of saidanode groups being arranged within the grids, the other of said anodegroups being arranged outside the grids.

References Cited in the file of this patent UNITED STATES PATENTS2,111,625 Heising Mar. 22, 1938 2,424,289 Snyder et al July 22, 19472,470,732 Visschcr May 17, 1949 2,472,779 Selgin June 7, 1949 2,615,142Adler Oct. 21, 1952

